1. Field of the Invention
The present invention relates generally to a vehicular power unit supporting device. More particularly, the invention relates to a vehicular power unit supporting device in motorcycles or the like whereby the propagation of engine vibrations to the vehicle body is minimized through a linkage.
2. Description of Relevant Art
There have been known motorcycles or three-wheeled motor vehicles having one front wheel and two rear wheels or vehicles of a similar construction wherein a power unit is constructed by integrating an engine with a transmission case which incorporates transmission means such as a chain for transmitting the engine power to the rear wheel, and the power unit which supports the rear wheel is suspended from a vehicle body frame through cushion means. In vehicles of such a construction, the front portion of the power unit is connected to the vehicle body frame and is supported thereby. It is necessary for a power unit supporting device to have high rigidity in the longitudinal direction of the vehicle body so that the driving force and braking force may be transmitted from the power unit to the vehicle body at the time of start-up, deceleration and acceleration, and also to have high torsional rigidity for preventing torsion from occurring in the transverse direction of the vehicle body between the vehicle body frame and the power unit. In the vertical direction, such rigidity should be minimized so that the engine vibration caused by operation of an engine having an exciting force acting in the vertical direction can be absorbed to prevent it from being propagated from the power unit to the vehicle body.
For absorbing and shutting-off the propagation of engine vibration from the power unit to the vehicle body, it has heretofore been known to connect a power unit to a vehicle body frame and thereby support it through a link mechanism such as a double link having two hinged joints. In this case, however, end portions of the link are connected through a rubber mount to the vehicle body frame and power unit, and because the rubber has resiliency in all directions, it is difficult to enhance rigidity in the longitudinal direction of the vehicle body and in the torsional direction. Therefore, it has been necessary to provide a rubber mount having a spring rate capable of satisfying the required rigidity in the aforesaid directions.
The present invention effectively overcomes the foregoing problems attendant the conventional vehicular power unit support device.